In dentistry, implants are used to replace missing teeth elements. This is carried out by drilling a cavity into the jawbone into which the implant is securely screwed or pressed. A dental prosthesis or crown is subsequently placed on the part of the implant that protrudes above the gums. Implants made of titanium have long yielded excellent results as far as durability and reliability are concerned. A drawback of using titanium implants, which are grey in colour, is the fact that titanium implants in many cases show through at the front on account of the edge of the bone which is locally thin there. Metallic edges also in many cases become visible over the course of time at the level of the line dividing the crown from the implant. In addition, research indicates that ceramic particles cause less inflammation and bone resorption than titanium particles; see Ichikawa Y., Akagawa Y., Nikai H., Tsura H., Tissue comptability and stability of a new zirconia ceramic in vivo, Journal of Prosthetic Dentistry 1992:68:322-326 and Warashina H., Sakano S., Kitamura S. et al., Biological reaction to aluminia, zirconia, titanium and polyethylene particles implanted onto murine calvaria, Biomaterials 2003:24:3655-3661. In order to eliminate these drawbacks of the often disappointing aesthetics and to utilize the advantages of better biocompatibility of ceramic, implants made of zirconium oxide have been developed. The current-day zirconium material has a high bending force (900-1,200 MPa), a Vickers hardness of (1,200) and a Weibull modulus of (10-12), making it a suitable material to make dental implants from. See for example “Survival rate and fracture resistance of zirconium dioxide implants after exposure to the artificial mouth”: An in-vitro study, inaugural dissertation Freiburg 2006, Andreiotelli M. and Oliva J., Oliva X., Oliva J D, One year follow-up of first consecutive 100 zirconia dental implants in humans: A comparison of 2 different rough surfaces, Int. J. Oral Maxillofac Implants 2007:22:430-435. There are currently various commercially available zirconium oxide implants which have to date been one-part implants such as Z-look3® and Sigma®.
However, just as in titanium implants, developments in zirconium oxide implants are tending toward two-part implants. A two-part implant allows the practitioner to choose. If the quality of the jawbone allows an insertion force of greater than 45 Ncm, the implant has sufficient primary stability to load it directly with a construction and a temporary arrangement. This is very important for patients on account of the aesthetic aspect in the replacement of front teeth. See in this regard example: “Clinical study on the primary stability of two dental implant systems with resonance frequency analysis”, Rabel, Annette1; Köhler, Steffen; Schmidt-Westhausen, Andrea, Clinical Oral Investigations, Volume 11, Number 3, September 2007 and “Immediate function with dental implants, Ho, C. C. K, Dental Practice, March/April 2005”. If this is not the case, then the loading can be delayed until the moment that the insertion part, covered by the gums, has first grown sufficiently together with the jawbone, that is to say is sufficiently osseointegrated. The force (Ncm) at which the implant can be brought into the jawbone is, beside good jawbone quality, very important. Now, a problem with zirconium oxide implants is the brittle material which soon breaks in the case of an excessively high force and/or in the case of a disadvantageously distributed force.
Two-part titanium implants are brought into the jawbone by means of an insertion instrument which is fed into the cavity of the insertion part. The insertion instrument can in this case be operated manually or else be clamped in a drilling machine. See in this regard for example the insertion instruments and the way in which the insertion parts are thus brought into the jawbone in the case of known two-part titanium implants for example Biomet 3i®, Nobel Biocare® and Straumann®. However, in the case of a zirconium-like insertion part, in particular in the case of insertion parts which have a cross section of 4 mm or less and are often used in the thin jawbone when replacing front teeth, the force which is exerted with an insertion instrument which is fed into the cavity is very soon too high. That is to say, the thin walls of a zirconium-like insertion part are unable to withstand, or have difficulty withstanding without breaking, the outwardly directed force which is for example greater than 30 Ncm. Furthermore, if the implantologist does not secure the instrument in an optimum position, i.e. perpendicularly above the insertion part, during the insertion, the force is increased still further as a result of the leverage and also distributed disadvantageously over the walls of the insertion part, as a result of which the insertion part breaks at the level of the neck. Premature breaking during the insertion of an implant is much less common in one-part zirconium-like implants because such implants are not internally hollow or weakened by a different connecting geometry. These implants are brought into the jawbone by means of an all-encompassing sleeve-like instrument; this is slid over the implant.